Coaxial cable linear delay line process

ABSTRACT

A DELAY LINE CONSISTING OF MULTIPLE TURNS OF METAL-JACKETED COAXIAL CABLE IS MANUFACTURED BY WINDING A COIL OF INSULATED WIRE AND PLATING A CONTINUOUS LAYER OF METAL AROUND THE COIL AND WITHIN THE INTERSTICES BETWEEN THE TURNS THEREOF.

June 8, 1971 J. w, HOLLAND EI'AL 3,583,065

COAXIAL CABLE LINEAR DELAY LINE PROCESS Filed NOV. 21, 1966 wn-zm 17/617, fi t /Z11; mafia/5 2 7961 6 United States Patent ()ffice 3,583,065 Patented June 8, 1971 US. Cl. 29-600 2 Claims ABSTRACT OF THE DISCLOSURE A delay line consisting of multiple turns of metal-jacketed coaxial cable is manufactured by winding a coil of insulated wire and plating a continuous layer of metal around the coil and within the interstices between the turns thereof.

This invention relates to delay lines and more specifically to coaxial cable linear delay lines and to methods of making such delay lines.

The amount of delay occasioned an electrical signal by a coaxial cable linear delay line is directly proportional to the length of the cable. To construct such a delay line, a desired length of insulated conductor is chosen and a metal jacket is drawn or swedged over the insulation to form a coaxial cable. This cable is then formed into the desired coil shape to create a delay line.

Several disadvantages exist for this type of construction. It is necessary to insert shorting straps between each turn of the coil to contact the metal jacket and effect a shorting bridge between each turn. If this is not done, the delay line will have excessive inductance. The drawing or swedging of a metal jacket cannot be accomplished on metal jackets less than 0.01 inch in wall thickness thereby resulting in a rather heavy delay line. Further with the drawn or swedged metal jacket, a coil cannot be constructed which is tightly formed since the bending radius thereof is limited, nor can a small size delay line be constructed. In fact, coaxial cable linear delay lines as presently existent are quite bulky and generally require lacing or resin encapsulation to retain their original shape. Such coils are also rather expensive to manufacture.

It is therefore one object of the present invention to provide an improved coaxial cable linear delay line and method of manufacture therefor.

It is another object of the present invention to provide a lightweight coaxial cable linear delay line and method of manufacture therefor.

It is another object of the present invention to provide a method for constructing a smaller coaxial cable linear delay line than heretofore possible.

It is another object of the present invention to provide a coaxial cable linear delay line which is characterized by more turns per area than heretofore.

It is another object of the present invention to provide a coaxial cable linear delay line which is characterized by ease of manufacture and low cost.

Other objects of the present invention will become more apparent as the detailed description proceeds.

Further understanding of thepresent invention may best be obtained from consideration of the accompanying drawing wherein:

FIG. 1 is a sketch of a circular coil delay line constructed according to the present invention.

FIG. 2 is a sketch of a rectangular coil delay line constructed according to the present invention.

FIG. 3 is a cross section of the coil of FIG. 1 constructed according to one method of the present invention.

FIG. 4 is a cross section of the coil of FIG. 3 after construction according to the present invention.

In FIGS. 1 and 2 typical shapes of coaxial cable linear delay line coils constructed according to the present invention are shown. Each delay line coil is constructed using an inner conductor 10 having an insulating coating 12 thereabout. Metal is plated over the insulating coating 12 and between the interstices of the coil to effect a continuous metal coating 14 about and between the turns of the coil.

In constructing the coils of FIGS. 1 and 2, the surface of insulating coating 12 generally must be treated to permit the plating of metal thereto. In the present invention, a conventional method of treating the surface of insulating coating 12 is followed, with the coating 12 first being etched to roughen the surface thereof. Etching is accomplished by a number of known ways depending upon the material of the insulating coating 12. For example, for Teflon, sodium etching is employed and for polyethylene, flame etching is employed. The etched insulating coating 12 is then is subjected to a sensitizing process to make the insulating coating 12 hydrophilic. The sensitizing process comprises immersing the insulation in a stannous chloride solution. The insulating coating 12 is then activated by immersion in a palladium chloride or gold chloride solution whereby monomolecular deposition of gold or palladium is elfected upon the insulating coating. With the insulating coating 12 thus treated, it can then be metallized.

The treating insulating coating 12 is metallized by electroless plating whereby a very thin continuous coating of metal, such as silver, copper or gold, is deposited on the coating 12. The inner conductor 10 is then formed, using conventional winding techniques, into the desired delay coil shape. After winding, the coil is electroplated using conventional electroplating techniques to deposit an appreciable amount of metal (from .001 to .005 inch) about the insulating coating 12 and between the interstices of the turns of the coil so that effectively a continuous metal coating exists throughout the coil.

The electroless metal coating prior to forming of the coil as recited supra insures that as each turn is wound, no insulation to insulation contact shall occur and that a continuous metal coating will be generated for the entire delay line coil. It is to be noted that an alternate method of constructing the delay line may be effected within the spirit of the present invention.

Turning to FIG. 3, such an alternate construction is shown for a multiturn multilayer delay line coil. The cross sections of the coil in FIGS. 3 and 4 are shown exaggerated to illustrate the spacing between coil turns. In this method of construction, the insulating coating is first etched and then the conductor 10 is formed into the desired delay line coil shape. Simultaneously with the winding of the coil, thin metal strips 18 are interwoven between adjacent turns of the coil to insure noncontact between adjacent insulating coatings 12. As shown in FIG. 3, wherein the turns are Wound vertically, it is not necessary that metal strips 18 be woven to completely encircle each turn of the coil. It is only necessary that the metal strips 18 encircle turns in each alternate vertical layer and partially encircle turns in the other vertical layers. As each turn is wound on the form, the metal strip is interwoven thereabout. It is to be understood that interweaving of metal strips 18 is accomplished at a sufficient number of circumferential points of the delay coil to insure that no insulation to insulation contact occurs in the turns thereof.

When the conductor 10 has been wound into the desired coil shape with the metal strips 18 interwoven therein, the coating 12 is sensitized by immersing the coil into a stannous chloride solution whereby the insulating coating 12 is made hydrophilic. The coil is then immersed in a palladium chloride or gold chloride solution to activate the insulating coating -12 and deposit thereon a monomolecular deposition of gold or pallidium. After activation, the coil is then metallized by electroless plating with a desired metal to effect a continuous thin metal coat about the insulating coating 12. An appreciable coating of desired metal (from .001 to .005 inch) is then deposited by conventional electroplating techniques about the insulating coating 12 and between the interstices of adjacent turns. This results in a coil substantially as shown in FIG. 4, the plated metal being of the same material as the metal strips 18.

With the aforementioned coil construction, a lightweight, smaller coaxial cable linear delay line may be manufactured than heretofore possible. Further, the type of construction permits delay lines to be manufactured in a variety of shapes without difficulty. The metal plating of the delay line coil serves not only as an outer conductor for the coaxial line and as a positive shorting bridge between turns but also as a potting medium enabling the coil to retain its manufactured shape without further operations thereon. Thus, a coaxial cable linear delay line coil is obtained which is characterized by case of manufacture and lower cost.

Persons skilled in the art will of course readily adapt the teachings of the present invention to embodiments and methods far diiferent than those described and illustrated above. Accordingly the scope of protection afforded the present invention shall be determined only in accordance with the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of manufacturing a delay line comprising forming an insulated wire into a predetermined coil shape, and plating a continuous metal coating about said insulated wire and within the interstices of said coil, wherein forming said coil comprises winding said insu- 4 lated wire into said desired coil shape and simultaneously therewith interweaving a metal strip between adjacent turns of said coil to maintain a spatial relationship therebetween.

2. A method of manufacturing a delay line as set out in claim 1 wherein said forming step also comprises plating a thin metal film on substantially the entire surface of the insulation of said wire preparatory in the winding step.

References Cited UNITED STATES PATENTS 2,552,999 5/1951 Pannel et al. 29-605X 3,201,854 8/1965 Cox 29-605 3,317,330 5/1967 Livingston et al. 204-30UX 2,397,568 4/ 1946 Seaman 29-600UX 2,887,764 5/ 1959 Knoll et al 29-600UX 2,982,703 5/1961 Noland 29-601UX 3,292,164 12/1966 Wells et al. 29-600UX 1,200,352 10/1966 'Hadaway, Jr 29-600UX 2,842,746 7/1958 Jones 333-29 2,892,162 6/1959 Bennett 333-29 2,894,221 7/1959 Coy 333-29 2,949,585 8/1960 Katz 333-29 3,312,773 4/1967 Lit 29-624 3,373,244 3/1968 Holland 29-624 3,131,460 5/1964 Allen 29-624 FOREIGN PATENTS 85,713 3/1895 Hungary 204-3 JOHN F. CAMPBELL, Primary Examiner R. W. CHURCH, Assistant Examiner US. Cl. X.R. 

